Device for keeping up oscillations of electromagnetic oscillators

ABSTRACT

An electrical device for sustaining the oscillations of an electromagnetic oscillator having an oscillating wheel-shaped element capable of reciprocal movement is disclosed. A fixed frame cooperating with the wheel-shaped element is positioned in the same plane as the element and has a pair of coils associated therewith for causing motion to be imparted to the element. The coils are connected in an electrical circuit containing an electronic switch and an electrical source. The electronic switch includes a control transistor which avoids the need for frictional contacts. The function of said device depends on the magnetic remanence of a deformable magnetic circuit formed by the element and the frame to produce reading and driving signals.

United States Patent Michel Emil Leon Havot; Guy Gustave Lucien Dubot. both of Dieppe.

I72] inventors France [2]] Appl No 818.038 [22] Filed April. 1969 [45] Patented [73] Assignee July [3. i971 Soclete Anonyme: Reveils Bayard Saint Nicolas DAlierlnont, Seine Maritime.

France [32] Priority Nov. 24, 1966 [33] France [3 l 84909 Continuation of application Ser. No. 684,060, Nov. [7, 1967.

[52] US. Cl .i

[51] lnt.C'l.i H03bS/30 l50| FleldolSearch. t t i t t, 33l/ll6, 154 l56; 58/23 Primary Examiner-John Kominski Attorney Baldwin. Wight. Diller and Brown ABSTRACT: An electrical device for sustaining the oscillations of an electromagnetic oscillator having an oscillating wheel-shaped element capable of reciprocal movement is disclosed. A fixed frame cooperating with the wheel-shaped element is positioned in the same plane as the element and has a pair of coils associated therewith for causing motion to be imparted to the element. The coils are connected in an electrical circuit containing an electronic switch and an electrical source. The electronic switch includes a control transistor which avoids the need for frictional contacts The function of said device depends on the magnetic remanence ofa deformable magnetic circuit formed by the element and the frame to produce reading and driving signals.

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PATENIEU JUL 1 31911 SHEET U 0? 4 DEVICE FOR KEEPING UP OSCILLATIONS F ELECTROMAGNETIC OSCILLATORS This is a continuation-in-part application of our copending application Ser. No. 684,060, filed Nov. l7, i967 entitled DEVICE FOR KEEPING UP OSClLLATlONS OF ELEC- TROMAGNETlC OSCILLATORS.

This invention relates to an electrical device for sustaining the oscillations ofelectromagnetic oscillators, such as the type which may be used in electrically driven chronometers which do not rely on the use ofso-called permanent magnets.

Prior art sustaining devices for electromagnetic oscillators associated with a deformable magnetic circuit comprise at least one contact means controlled by the oscillator itself. Such contact means has inherent defects despite the care taken in manufacture, and in addition said means is subject to wear in the course of time, leading to malfunctioning of the oscillator.

Sustaining devices for oscillators comprising permanent magnets are also known which contain contact means or a transistor and in which permanent magnets or electromagnetic windings are disposed on the regulating system which controls the regulating pulses for sustaining the oscillations. When permanent magnets are disposed on the regulating means, it is difficult to obtain an optimum quality factor because the additional masses create an unfavorable ratio between the moment of inertia and the mass of the regulating means in addition, friction, such as viscous drag, may also contribute towards reducing the quality factor. When mounting coils on the regulating system, very delicate problems of design and manufacture are encountered.

The invention makes use of the remanance of a deformable magnetic circuit to provide, by means ofa coil, a signal which is subsequently used to initiate a driving pulse to be applied through a control transistor for maintaining oscillation of the electromagnetic oscillator.

The sustaining device mentioned above includes a driving coil and a reading coil both of which may be formed on the same fixed armature which forms part of a deformable magnetic circuit. The passage of an initial pulse of energy passing through the driving coil produces. in the reading coil, a voltage which is supplied to a switching transistor. The magnitude of the voltage is such that the gain of the transistor, multiplied by the coupling of the two coils, is higher than unity.

in other words the flux resulting from the magnetornotive force, which is produced in the magnetic circuit by the initial pulse of energy, must induce in the reading coil a voltage higher than the saturation voltage of the transistor in order to maintain the transistor in a saturation state of conduction. The latter state lasts throughout the time during which variation of the flux is sufficiently great to induce the voltage in the reading coil.

In practice the voltage produced by the reading coil does not exceed 50 mv., whereas the base saturation voltage of transistors of the silicon type is approximately 700 mv. Therefore, when such transistors are used it is necessary to provide means to amplify the induced voltage in the reading coil.

To meet this requirement the base of the transistor is earthed through the winding of a transformer or an autotransformer, a tapping of which is connected to an intermediate point of a coil formed on a fixed pole in the magnetic circuit. One end of the coil is earthed, while the other end is connected to the emitter of the transistor. The collector of the transistor is connected to a potential source. The number of turns between those portions of said windings between the two tapping points and earth is shown to establish an amplification ratio with the number of turns between the two tapping points and the points of connection of said windings to the transistor. The coil formed on the fixed pole serves both as the driving winding and the reading winding.

Under certain conditions this amplifier arrangement may behave as an oscillator unless precautions are taken, also the emitterbase function of the transistor may be disturbed by an induced inverse voltage arising in the driving coil and that portion of the autotransformer between the tapping point and earth.

It is a primary object of the present invention to provide an electrical device which does not contain frictional electrical contacts, and which sustain the oscillation of a movable element of an electromagnetic oscillator, by utilizing the remanence of a deformable magnetic circuit to produce a reading and a driving signal which cooperate to cause said oscillation.

It is a further object of the present invention to provide an electrical device for sustaining the oscillation of a movable element of a contactless electromagnetic oscillator, and having a regenerative electrical circuit comprising a reading and a driving coil located in such a manner in a deformable magnetic circuit, as to produce a reading and a driving signal which cooperate to impart an accurate and a stable oscillation to said movable element.

It is an additional object of the present invention having the above mentioned features, to provide amplifying means incorporated in said device for amplifying said reading signal to a value necessary for the operation of certain transistors when used as a switching element in said device.

it is another object of the invention to provide a simple and accurate, contactless, electromagnetic oscillator which may be used as the timing mechanism in a chronometer.

It is a still further object to overcome the tendency of the amplifier to behave as an oscillator and to avoid undesirable induced inverse voltage arising in the driving coil and autotransformer from disturbing the emitter-base function.

The sustaining devices of the prior art do not give the ideal sustaining conditions in which the period of the oscillator is undisturbed by a so-called instantaneous pulse transmitted through the regulating means or balance wheel near the dead center ofits movement.

The invention has the aim of obviating the disadvantages of previous devices by providing a device for sustaining the oscillations of regulating and/or driving impolarized electromagnetic oscillators, particularly low frequency oscillators. The use of such oscillators in the field of chronometry is particularly advantageous, due to the feature of ensuring the increased stability of sustained oscillations in a timepiece.

The invention essentially takes advantage of the phenomenon of remanence of deformable magnetic circuits. It is in fact known that any mechanical oscillator, and particularly any low frequency oscillator utilizing a deformable magnetic circuit, has a remanence value which depends, amongst other factors, on the quality of the materials used in the circuit, such as ferronickels, and the size of the air gaps, the remanence being the higher, the smaller the air gaps.

The invention is based on the fact that is possible to use the property of remanence in order to obtain by means ofa coil, a signal which can be used for controlling the driving pulse of the sustaining device.

In its most general form the device of the invention has a regulating means which is associated identical with the previously a deformable magnetic circuit to which a control pulse is applied by means of a transistor. Further, the device comprises at least one coil, hereinafter referred to as a driving coil, and which is associated with a fixed pole of the magnetic circuit, at least one other coil, hereinafter referred to as a receiving or reading cr il, and which is associated with a fixed pole of the circuit which may be identical with the previously mentioned pole. The driving coil is connected between a source of low tension direct current and the collector ofa transistor, the reading coil is connected between the base of said transistor and ground, and the emitter of the transistor is connected to earth.

The deformable magnetic circuit is preferably composed of two parts, namely a fixed part and a movable part which cooperate in the same plane. This arrangement in fact offers practical advantages, because the magnetic circuit can thus be made accurately and at low cost.

The operating signal is transmitted to the transistor by the reading coil, and the transistor serves as a switching transistor. The driving coil and the reading coil may be mounted on the same fixed pole of the magnetic circuit, or each of said coils may be on separate fixed poles. The flux resulting from the magnetomotive force must induce in the reading coil a voltage which when applied to the base of said transistor, will cause the emitter/collector junction to change from a state of high impedance to a state of low impedance, said state of low impedance lasting throughout the time during which the variation of flux is sufficiently great to induce said voltage. In other words, said flux must induce a voltage in the reading coil which is greater than the saturation voltage of the transistor in order to maintain said transistor in a saturation state of conduction.

However, in many cases, the reference reading voltage does not exceed 50 mv., whereas the base saturation voltage of transistors of the silicon type is closed to 700 mv. In such cases it is, therefore, necessary to use a transformer element having voltage input to output ratios close to l: to obtain the required 700 mv. from a low induced voltage in the reading coil.

In a preferred embodiment of the invention an arrangement is provided to amplify the induced voltage in the reading coil. The base ofa transistor is connected to the mass of the oscillator apparatus serving as a ground connection, through the winding of an autotransformer, an intermediate tapping of which is connected to an intermediate point of a coil wound on a fixed pole of the magnetic circuit of said apparatus. One end of said coil is connected to said mass, and the other end is connected to the emitter of the transistor. The collector of the transistor is connected to an electrical supply of the oscillator. The intermediate tapping of the autotransformer is determined by the ratio of a number ofturns between the mass of the oscillator and said tapping, and the number of turns between said tapping and the base of the transistor, which ratio is chosen so as to give the required amplification of the induced voltage in the reading coil. The tapped coil wound on the fixed pole of the magnetic circuit serves both as the reading and the driving coil.

In one form of construction the device comprises a single coil constituting the reading element and driving element, a voltage transformer amplifying the voltage induced in said coil by the remanent magnetic potential of the circuit, a switching transistor which is connected with its collector under load and the emitter of which is earthed, its base being fed by the secondary of said transformer, shunted by a diode, while the primary of said transformer is connected in series with a resistorcapacitor cell which is in turn connected in parallel on the winding ofsaid coil.

It is obvious that the device described above may comprise numerous forms of construction which come within the framework of the invention. The detailed description below has the object of illustrating the essential characteristics ofthe invention, while providing those versed in the art with means for determination suitable for their particular requirements. This description will be given with reference to the accompanying drawings, in which:

FIG. I is a diagram illustrating the device proposed by the invention;

FIG. 2 shows the electronic circuit associated with the device illustrated in FIG. 1;

FIGS. 3, 4 and 5 are diagrams illustrating the operation of the device shown in FIG. 1;

FIG. 6 is a plan view of the regulating means and of the fixed part of the magnetic circuit in one embodiment of the invention and in a position corresponding to the moment of the triggering ofthe signal;

FIG. 7 illustrates another position ofthe regulating means of the device shown in FIG. 6',

FIG. 8 illustrates an arrangement effecting the amplification of the reading voltage;

FIG. 9 illustrates an arrangement including an electronic circuit effecting amplification ofthe reading signal; and

FIG. I0 illustrates an alternative form of the circuit arrangement shown in FIG. 9.

A magnetic circuit may be characterized by its permeance, or its reluctance. By analogy with an electric circuit, the reluctance of the magnetic circuit corresponds to resistance. There is a known law which relates the permeance P ofa magnetic circuit to the inducing flux in the circuit and to the magnetomotive force M. This law is written as follows:

It is in addition known that the reluctance ofa magnetic circuit is equal to the sum of the reluctances of the different elements of which said circuit is composed, and in a general way to the total of the reluctance of the iron circuit and the reluctance of the air gaps.

In the case ofa deformable magnetic circuit the reluctance in an open circuit is equal to that of the air gap and consequently has a very high value. When the circuit is closed, provided that the air gaps are very small, the permeance of the magnetic circuit increases considerably.

Reference will now be made to FIG. I, which illustrates diagrammatically the deformable magnetic circuit which is composed ofa regulating means or movable armature 1 associated with a fixed frame 2 which comprises two armatures at the poles 3 and 4. The regulating means I is a balance wheel which oscillates about a pivot 5. The regulating means 1 is separated from the poles 3 and 4 by small air gaps. The rotational displacement of the regulating means I will hereinafter be indicated by the angle a between the straight line joining the pivot 5 to the movable pole 6, and the line joining the longitudinal axis of the armature 4, to the center of the pivot 5.

A driving coil 7, containing a plurality of turns equal to N, and a reading coil 8, containing a plurality of turns equal to N, are wound around the same fixed armature 4.

The wheel I and the frame 2 preferably cooperate in the same plane and are produced by stamping or cutting from a solid sheet. The windings 7 and 8 are made on the same core are in part wound together. The coils 7 and 8 are advantageously disposed in the immediate proximity of the pole 4a of the fixed armature 4. The pole 3 enables magnetic lines of force to pass through the frame 2 and the wheel 1.

The coils 7 and 8 are inserted in an electric circuit arrangement which is partly illustrated in FIG. 2. The driving coil 7 is connected to a source 9 oflow voltage direct current, one pole of which is grounded at I]. A switching transistor 10 contained in the circuit, has its emitter grounded at II, and the driving coil 7 as a collector load, and the reading coil 8 connected between its base and the ground 11.

The operation of the invention will now be described in detail.

FIG. I shows that magnetic circuit may be deformed by the angular displacement of the regulating means 1 in relation to the fixed frame 2. The variation of the permeance P of the circuit is therefore a function of the variable a, which represents the angular displacement of the movable poles from the fixed poles. It will however be shown that it is more advantageous to indicate the variation of P with a by using the derivative form (dp/da). because P is a complex function ofa plurality ofvariables such as the permeability of the materials used, and the geometrical shape of the magnetic circuit.

It can in fact be shown that the couple transmitted during a pulse to the regulating means I is of the form K(dP/ do) where K is a constant, when the magnetomotive force is constant.

When a pulse has been applied, there remains in the magnetic circuit a remanent induction B, of which the lines of force are indicated in broken lines at 2' in FIG. I. The remanent induction Brgives rise to a remanent flux 1), which is proportional to the permeance P of the circuit (P' is different from the permeance P because the circuit has been deformed) and also to the remanent magnetic potential V,. The relation can, therefore, be expressed:

%=KV P' (2) where K is a constant.

The flux l consequently induces in the reading coil 8 (number ofturns N) a voltage e (FIGS. 1 and 2) the value of which is given by the relation:

A simple calculation shows that we can put 2 in the following form:

have the meanings indicated above, K" is a constant, and a is the derivative of the angle in relation to time.

It is therefore seen that the reading signal e induced in the coil 8 is proportional to the expression (dP'l do).

In other words, the source 9 (current I) induces in the driving coil 7 a driving signal which is proportional to (dP/da) and, after the pulse, the remanent flux induces the reading coil 8 a signal which is known as the reading signal and which is proportional to (dP'! do).

The operation of the diagrammatical circuit shown in FIG. 2 will now be briefly described.

In the state of rest the base of the transistor is at the same potential as the emitter and consequently the transistor 10 is blocked. The voltage e produced in the reading coil 8 after the passage of a pulse is such that the gain of the transistor I0, multiplied by the coupling coefficient of the coils 7 and 8, is higher than unity. It should also be noted that the load impedance must have a high value, taking into account the form of the reading signal, thereby promoting a rapid change in the gain of the circuit. In these circumstances the transistor 10 becomes conductive Consequently, the current I increases exponentially in the driving coil 7. In addition the flux resulting from the magnetomotive force induces in the reading coil 8 a voltage higher than the saturation voltage of the transistor 10 which therefore remains conductive. The state of saturation lasts l.oughout the time during which the flux variation is sufficiently great, which time can be regulated in a known manner by the selection of the time constant of the driving winding.

FIGS. 3 to S are diagrams illustrating the shape of the signals which can be obtained in a sustaining device of the type illustrated diagrammatically in FIGS. 1 and 2.

The three graphs in FIGS. 3 to 5 represent respectively the variations of e,(dP/daand I, in dependence on the angle a and assuming that the latter is a sinusoidal function of time corresponding to an alternating displacement of the regulating means I. It is obviously interesting to study all three of these graphs with the corresponding values of or.

The signal e is induced in the reading coil 8 for a very small change A a, in the angle a, where 0:, corresponds to the angle at which the transistor 10 becomes conductive, and the current I starts to flow in the driving coil 7. The variation of the signal e with the angle a is shown by FIG. 3, the maximum value e,,, of: being obtained at angle a.

FIG. 4 illustrates the relationship between the rate of change of perrneance P with at, Le. (dP/da) and the angle a. The maximum value of dP/ do) occurs at our: which lies between the angles a and a, where the interval of time between a, and a, corresponds to the time during which the current I flows in the driving coil 8.

FIG. 5 illustrates the relationship between the current I in the driving coil 8 and the angular displacement or of the regulating means I.

The operation of the device of FIG. I, is largely dependent on the parameters P and (dP/da). In particular a necessary condition is that the interval between or to a, should be centered around the value o which corresponds to the maximum value of (dP/ da. The means of achieving this result is to create an angular phase shift between the reading pole or poles and the driving pole or poles. This phase shift of value 0 may be known because it is linked to the time constant of the circuit.

These various factors are essential and may be determined in each particular case from the natural characteristics of the circuit. These characteristics can in fact be selected so as to obtain graphs of the type illustrated in FIGS. 3 to 5 by determining the values of the magnetic permeability, the time constant of the circuit, and so on.

These advantageous operating conditions are those under which the reading signal e is very short (corresponding to a very low angular change A0,), thus enabling the pulse to be triggered with great accuracy.

It will also be noted that because of the energy absorption of the device the variation (dP/da) is obtained over a wider angular range than for (dP'lda All these conditions are advantageously fulfilled by the device illustrated in FIGS. 6 and 7, which is an alternative form of construction of the invention.

The device illustrated in FIGS. 6 and 7 is one of the possible embodiments of the basic diagram shown in FIG. I. It contains a balance wheel or regulating means 21 associated with a fixed frame 22. The devices 2! and 22 together form a deformable magnetic circuit the movable part 21 and the fixed part 22 of which cooperate in the same plane. The parts may be obtained by die stamping in pure treated iron and have the shape illustrated in the drawings.

The fixed circuit 22 contains four poles 23, 24, 29, 30. and a reading coil 28 and a driving coil 27. The coil 28 is disposed around the armature 24 in the immediate proximity of the active pole. Similarly, the coil 27 is disposed around the armature 29 in the immediate proximity of the active pole.

The wheel or regulating means 2! is mounted for rotation about a pivot 25 and has two poles 26, 31 separated by a slot 32.

The fixed pole 24 and the movable pole 26 are intended to produce the reading signal.

The fixed pole 29 and movable pole 31 are intended to be polarized by the driving signal.

The fixed pole 30 is intended to shunt the magnetic circuit when the wheel 21 is in certain angular positions.

The pole 23 is a field closure pole having a wide shoe, extending over a large angle.

The air gaps separating the fixed poles 23, 24, 29, 30 from the periphery of the wheel 21 are of the order of 0.06 to 0.1 mm. These low tolerances may be obtained without difficulty in the manufacture of the parts, because the moving and fixed parts of the deformable magnetic circuit cooperate in the same plane.

The small air gaps and the arrangement of the fixed armature create a magnetic circuit of very low leakage.

The reading coil 28 contains approximately 7000 to 8000 turns wound with a wire offrom 0.04 to 0.05 mm. in diameter. The driving coil 27 comprises from 3000 to 4000 turns wound from a wire ofa diameter of0. l 2 to 0.14 mm.

The device illustrated in FIGS. 6 and 7 is inserted in an electrical circuit of the type illustrated in FIG. 2. The source 9 may be a 1.5 volt source. The transistor 10 is of the high speed switching, low leakage current, germanium type. Its gain is higher than and its breakdown voltage between emitter and collector is 20 volts. Some conventional improvement may be made to the electrical circuit used with the device shown in FIG. 7. For example, a switch may be provided between the transistor l0 and the ground 11. It is so interesting to install at the terminals of the driving coil 27 (reference 7 in FIG. 2) a capacitor of low value, or a diode, to short circuit the break impulse produced on the discharge of the coil.

The study of the characteristics of the device illustrated in FIGS. 6 and 7 will be continued with the use of the same references as in FIGS. 3 to S.

The presence of the movable poles 26 and 31 on the wheel 21 makes it possible to obtain a reading signal over an angle A01 which differs from the angle between a and a, corresponding to the pulse time.

The reading pole 26, which has a projecting or stepped shape, produces a signal voltage e, close to 200 mv. The angle a, then corresponds to an interval of time of 50 pr. Theoretical calculation on the pole shape involves an equation containing inverse (hyperbolic) trigonometrical functions, the solution of which is difficult to resolve. The pole shape was, therefore, obtained experimentally by measuring the function (dP Ida) until the desired shape and width of the reading signal were obtained.

In FIGS. 6 and 7 the wheel 2! receives only one pulse over its oscillation in a clockwise direction as indicated by the arrow f, in the example of the device described.

FIG. 6 illustrates the position of the wheel 21 at the moment of triggering the reading signal, i.e., when the reading pole 26 is near the fixed pole 24, and when (dP'ldcr) is a maximum. The position of the moving pole 3] in relation to the pole 29 corresponds to the angle a, (FIG. 5) when current starts to 5 flow in the driving coil 27.

It will also be observed that in the position illustrated in FIG. 6, the pole 30 is situated opposite the slot 32 formed in the wheel 21, so that the lines of force of the remanent flux follow the path 22' shown in broken lines, while the lines of force of the magnetizing field are indicated in dot-and-dash lines 22". The air gap separating the pole 30 from the slot 32 is too great to permit the passage of the lines of force. In order to facilitate description, the position of the wheel ZI in FIG. 6 will be indicated by the angle 'y shown in the drawing.

FIG. 7 illustrates the wheel 21 in a position fl=(1r/ ZH-B, in which the moving driving pole 31 is situated in a position between the fixed poles 24 and 30. In this angular position further triggering is avoided by short-circuiting the changing flux induced by the driving coil 27, through the pole 30. The lines of force of the remanent field are indicated by the broken line 22'a and the lines of force of the magnetizing field by the broken line 22"a.ln this relative arrangement of the poles, the switching transistor remains nonconductive. 25

When the wheel 21 rotates in the clockwise direction, the sign of the signal e is reversed and the switching transistor remains nonconductive.

The embodiment which has with reference to FIGS. 6 and tions for sustained oscillation, low value (A001,) is centered balance wheel movement.

Other deformable magnetic circuits could naturally be conceived which do not depart from the scope of the invention, as long as they comply with the conditions indicated above.

FIG. 8 illustrates another alternative embodiment of the invention which enables the use of silicon transistors having a base saturation voltage close to 700 mv. Amplification means are provided for amplifying the reading signal voltage to the value required to saturate such transistors.

The regulating means I oscillating about the pivot 5 contains the element 6, constituting the pole which is movable in relation to the fixed poles 3 and 4 of the magnetic circuit 2. A coil 34 is wound on the fixed pole 4, one end of which is connected to the ground ll of the oscillator apparatus, and the other end is connected by a wire 35 to the emitter of the switching transistor I0. The collector of the transistor I0 is connected by a wire 36 to a potential source (not shown). The base of the transistor 10 is connected to the ground ll through the winding of an autotransformer 37, of which a point B of said winding is connected by a wire 38 to a point E of the coil 34.

It will be seen that in both a driving coil with part ED.

The voltage induced in the coil 34, and particularly that taken from its part ED, is fed to the input of the autotransformer 37 where it is amplified by an appropriate ratio of turns AB:BC to give a suitable voltage at the base of the transistor I0.

In an example of the above embodiment the coils 34 and 37 were made as follows:

Winding 37 Part AB about turns of 5/I00 mm. wire.

Part BC about 5000 turns of 5/1 00 mm. wire.

Winding 34 Part DE about 200 turns of I6/l00 mm. wire.

Part EF about 1800 turns of l6/l00 mm. wire.

The result is thus approximately as follows:

V V XQOI 2000 X(5000 /20 or V V where V, is the voltage of the signal at the base of the transistor 10, and V is the induced reading voltage.

just been described in detail 7 permits almost ideal condibecause a pulse angle of very around the dead center of the this arrangement the coil 34 serves as 5 its parts EF, and as reading coil with its FIG. 9 shows a regulating device I, for example, a balance wheel, which is mounted to oscillate about a pivot 5. The device I constitutes a pole or armature which is movable in relation to fixed poles 3 and 4 of a magnetic circuit 2.

Formed on the fixed pole 4 is a winding 34 one end of which is connected to an earth connection 11 of the apparatus, while its other end is connected by a lead 35 to the emitter of a switching transistor 10. The collector of the transistor 10 is connected by a lead 36 to a potential source (not shown). The base of the transistor I0 is connected to the earth connection II through the winding 37 of an autotransformer. A tapping point B of the winding 37 is connected by a lead 38 to a point E ofthe winding 34.

It will be seen that in this arrangement the winding 34 serves as both a driving coil with its part EF, and as a reading coil with its part ED.

A voltage induced in the winding 34, and in particular that taken from the part ED, is fed by the lead 38 to the input of the autotransformer winding 37, of which the part BC cooperates with the part EF to produce a considerably amplified reading signal.

inverse voltage may be formed by the winding 34 and the part BA of the winding 37 of the auto transformer.

To counteract these two disadvantages, a diode 39 is connected between the base and the emitter of the transistor 10 at points 10b and 10c respectively. This provision prevents the circuit arrangement from behaving as an oscillator and also protects the base-emitter function of the transistor II] by short-circuiting the induced inverse voltage.

FIG. 10 illustrates an alternative embodiment in which a single coil 41 serves both as a reading element and as a driving element.

A voltage transformer 42 amplifies that voltage induced in the winding of the coil 4| by the remanent magnetic potential produced in the circuit.

A silicon transistor 43, of the NPN ture, is connected with its collector under load, by a lead 44 to one end of the coil 41, and its emitter is connected by a lead 45 to an earth connection 46.

The base is fed through a lead 47 connected to one end of the secondary winding of the transformer 42 the other end of which is connected to the earth connection 46.

The secondary is shunted by a silicon diode forms four functions namely:

a. avoiding unwanted oscillation ofthe arrangement;

b. protection of the base-emitter function of the transistor c. temperature stabilization by head to tail connection with the base-emitter function;

d. reversal of remanent potential at the level of the active poles of the magnetic circuit.

The primary winding of the transformer 42 is connected in series with a resistor 49 in parallel with a capacitor 50. This combination is connected in parallel with the winding of the at one end by a lead 51 to a positive terminal 52, to which a lead 53 connects the other end of the primary of the transformer 42.

The resistor 49 is provided to maintain correct collector bias relative to the switching action of the transistor 42 which in turn is dependent upon the base current appearing in the secondary winding of the transformer 42. The capacitor 50 is connected as a shunt across the resistor 49 bypass transients in particular steep from reading voltage. The base bias is maintained at a voltage which approximates 700 mv. this being the magnitude of voltage necessary to maintain silicon transistors in a state of saturation.

In a practical construction of the device modified in this manner the following characteristics were given to its component elements:

The winding of the coil 41 l2/l000 millimeter.

type and of planar struc- 48, which percomprises 4000 turns of wire of The primary of the transformer 42 comprises 250 turns of wire of 22/100 millimeter, and the secondary comprises 5000 turns of wire of /1 00 millimeter.

The resistor 49 has a value of H100 and the capacity of the capacitor 50 is 0.5 mf.

The values set out immediately above are given only as a simple example without limitation and may be modified without thereby departing from the spirit of the invention.

This arrangement offers the advantage of permitting the use of a silicon transistor associated with a low remanence magnetic circuit, remanence always being prejudicial to the chronometric qualities and efficiency of time apparatus.

Whilst specific examples of the invention have been described herein, it will be understood that other alternative methods of using the invention may be apparent without departing from the scope of the following claims.

What we claim is:

1. An electromagnetic oscillator comprising in combination a movable and a fixed element, an electrical device for sustaining the oscillation of the movable element, said movahle and said fixed elements forming at least one deformable magnetic circuit the remanence of which is utilized in the function of said device, a reading and a driving coil, constituting part of said electrical device, said coils being mutually associated with one of two fixed poles of said circuit, an electronic switching element comprising a transistor having a base, and an emitter-collector junction the impedance of which depends on the value of a reading signal derived from said readin coil, and supplied to said base and wherein said reading coil is connected between said base and a ground, and said driving coil is connected is series with said emitter-collector junction, a direct source of electrical current, and said ground, said source inducing a driving signal in said driving coil whereby an electromagnetic force is applied between said driving coil and said movable element to impart motion thereto.

2. An electromagnetic oscillator according to claim I, in which said movable and said fixed element cooperate in the same plane.

3. An electromagnetic oscillator according to claim I, in which said direct source of electrical current induces the driving signal in said reading coil in the form ofa pulse of energy, and after said pulse the remanent flux in said magnetic circuit induces said reading signal in said reading coil, the inductions repeating in a respective sequence so as to maintain said oscillation.

4. An electromagnetic oscillator according to claim 1 in which said driving coil is connected between said direct source ofelectrical current and the collector of said transistor, said reading coil is connected between the base of said transistor and said ground, and the emitter of said transistor is connected to said ground.

5. An electromagnetic oscillator according to claim 1 in which said fixed element is a frame of ferromagnetic material, said fixed poles being made of ferromagnetic material and integral with and projecting inwardly of said frame; and said movable element is a balance wheel made of ferromagnetic material pivoted reciprocally to rotate within the boundaries oi said frame, and having at least one peripheral prominence which acts as a magnetic pole, and a radial spoke on each side of a central surface about which said wheel is pivoted; said prominence, said spokes and said surface forming part of a mutual path for two deformable magnetic circuits through said movable element, said frame and said fixed poles; and wherein said frame and said fixed poles form a substantially E- shaped member with a closure piece across the outer limbs so as to complete two other separate paths for said magnetic circuits; and wherein the clearance between the ends of said fixed poles and the periphery of said wheel is small enough to provide magnetic circuits of low leakage.

6. An electromagnetic oscillator according to claim 1, in which a diode is connected between the emitter and base of said transistor.

'7. An electromagnetic oscillator comprising in combination a movable and a fixed element, an electrical device for sustaining the oscillation of the movable element, said movable and said fixed elements forming at least one deformable magnetic circuit the remanence of which is utilized in the function of said device, a reading and a driving coil, said reading coil being associated with a first fixed pole of a first deformable magnetic circuit, and said driving coil being associated with a second fixed pole of a second deformable magnetic circuit, a third and a fourth fixed pole associated with a third and a fourth deformable magnetic circuit respectively, the third and fourth fixed poles each being situated on opposite sides of the fixed element and being between the first and second fixed poles, an electronic switching element comprising a transistor having a base, and an emitter collector junction the impedance of which depends on the value of a reading signal derived from said reading coil, and supplied to said base, and wherein said reading coil is connected between said base and a ground, and said driving coil is connected in series with said emitter-collector junction, a direct source of electrical current, and said ground; said source inducing a driving signal in said driving coil whereby an electromagnetic force is applied between said driving coil and said movable element to impart motion thereto.

8. An electromagnetic oscillator according to claim 7 in which said movable said fixed element cooperate in the same plane.

9. An electromagnetic oscillator according to claim 7 in which said direct source of electrical current induces the driving signal in said reading coil in the form of a pulse of energy, and after said pulse the remanent flux in said magnetic circuit induces said reading signal in said reading coil, the inductions repeating in a manner in a respective sequence so as to maintain said oscillation; said driving coil being connected between said direct source of electrical current and the collector of said transistor, said reading coil being connected between the base of said transistor and said ground, and the emitter of said transistor being connected to said ground.

ll]. An electromagnetic oscillator according to claim 7 in which said fixed element is a frame of ferromagnetic material, said fixed first, second, third and fourth poles being made of ferromagnetic material and integral with said frame, and said movable dement is a balance wheel pivoted reciprocally to rotate within the boundaries of said frame, and having at least two peripheral prominences spaced apart on the periphery of said wheel, the spacing of the projecting ends of said first and third fixed poles, and said wheel also having at least one open slot in its periphery located between said prominences in a position which causes said slot to be substantially adjacent the projecting end of the second fixed pole when said wheel is rotated so that said prominences are each adjacent the projecting ends of said first and third fixed poles, said first, second, third and fourth fixed poles forming respective paths for a plurality of deformable magnetic circuits passing through said frame and said wheel, and wherein said frame forms a continuous outer path, said fourth fixed pole is a substantially scimitar-shaped, integral portion of said outer path and extends over a distance corresponding approximately to a third of the periphery of the wheel, said first, second and third fixed poles projecting inwardly of said continuous outer path and terminating with a small clearance between the ends thereof and the periphery of said wheel, said clearance and the clearance between the fourth fixed pole and the periphery of the wheel being small enough to provide said magnetic circuits having low leakage.

H. An electromagnetic oscillator according to claim 7, in which a diode is connected between the emitter and base of said transistor.

12. An electromagnetic oscillator comprising in combination a movable and a fixed element, an electrical device for sustaining the oscillation of the movable element, said movable and said fixed elements forming at least one deformable magnetic circuit the remanance of which is utilized in the function of said device, a reading and a driving coil, constituting part of said electrical device. which device comprises a single tapped coil wherein the turns between one end of said coil and the tapping constitute said reading coil, and the turns between the tapping and the other end of said coil constitute said driving coil, said tapped coil being mutually associated with one of the fixed poles of said circuit, an electronic switching element which is a transistor having a base, and an emitter-collector junction the impedance of which depends on the value of a reading signal derived from said reading coil, and wherein one end of said tapped coil is connected in series with said emitter-collector junction, a direct source of electrical current, and a ground, the other end of said tapped coil being connected to said ground, an autotransformer constituting a single coil with an intermediate tapping, said coil being connected between the base ofsaid transistor and said ground, said intermediate tapping being connected to the tapping on said tapped coil; said intermediate tapping on said autotransformer being located such that the reading signal derived from the reading coil is amplified by a predetermined value by said autotransformer to generate a signal which when supplied to the base of said transistor causes the emitter-collector junction to become conductive, said source inducing a driving signal in said driving coil whereby an electromagnetic force is applied between said driving coil and said movable element to impart motion thereto.

13. An electromagnetic oscillator according to claim 12, in which a diode is connected between the emitter and base of said transistor.

[4, In a device for the maintenance of the oscillations of nonpolarized electromagnetic oscillators having a regulating unit associated with a deformable magnetic circuit to which a control pulse is applied through the intermediary of a silicon transistor, at least one motor coil associated with a fixed pole of the magnetic circuit; at least one reading coil, associated with a fixed pole of the circuit; the motor coil being mounted between a source of low voltage direct current and the collector of a transistor, the reading coil being mounted between the base of said transistor and the ground, the emitter of the transistor being grounded, the base of said transistor being connected to the mass of the electromagnetic oscillator through the winding of an autotransformer, the intermediary tap of which is connected to an intermediary point of a winding surrounding a fixed pole of the magnetic circuit, one of the extremities of said winding being connected to said mass while the other extremity is connected to the emitter of the transistor, the collector of which is connected to polarization elements of the oscillator, the first parts of the two above mentioned windings connected to the mass comprising a number of turns calculated to establish a specific amplification ratio with the number of turns of the second parts of the windings connected to the transistor, the winding surrounding the fixed pole of the magnetic circuit thus serving both as motor coil and reading coil.

[5. in a device according to claim 14, a diode inserted between the terminals of the base and of the emitter of the transistor between the motor coil and the autotransformer so as to prevent the amplifying unit from acting as an oscillator and to protect the emitter-base function of the transistor by short-circuiting induced reverse voltage originating in the motor coil and the portion of the autotransformer connected to the mass and located beyond the point ofjunction with said motor coil.

16. In a device according to claim 14, a voltage transformer amplifying the reading voltage. 

1. An electromagnetic oscillator comprising in combination a movable and a fixed element, an electrical device for sustaining the oscillation of the movable element, said movable and said fixed elements forming at least one deformable magnetic circuit the remanence of which is utilized in the function of said device, a reading and a driving coil, constituting part of said electrical device, said coils being mutually associated with one of two fixed poles of said circuit, an electronic switching element comprising a transistor having a base, and an emittercollector junction the impedance of which depends on the value of a reading signal derived from said reading coil, and supplied to said base and wherein said reading coil is connected between said base and a ground, and said driving coil is connected is series with said emitter-collector junction, a direct source of electrical current, and said ground; said source inducing a driving signal in said driving coil whereby an electromagnetic force is applied between said driving coil and said movable element to impart motion thereto.
 2. An electromagnetic oscillator according to claim 1, in which said movable and said fixed element cooperate in the same plane.
 3. An electromagnetic oscillator according to claim 1, in which said direct source of electrical current induces the driving signal in said reading coil in the form of a pulse of energy, and after said pulse the remanent flux in said magnetic circuit induces said reading signal in said reading coil, the inductions repeating in a respective sequence so as to maintain said oscillation.
 4. An electromagnetic oscillator according to claim 1 in which said driving coil is connected between said direct source of electrical current and the collector of said transistor, said reading coil is connected between the base of said transistor and said ground, and the emitter of said transistor is connected to said ground.
 5. An electromagnetic oscillator according to claim 1 in which said fixed element is a frame of ferromagnetic material, said fixed poles being made of ferromagnetic material and integral with and projecting inwardly of said frame; and said movable element is a balance wheel made of ferromagnetic material pivoted reciprocally to rotate within the boundaries of said frame, and having at least one peripheral prominence which acts as a magnetic pole, and a radial spoke on each side of a central surface about which said wheel is pivoted; said prominence, said spokes and said surface forming part of a mutual path for two deformable magnetic circuits through said movable element, said frame and said fixed poles; and wherein said frame and said fixed poles form a substantially E-shaped member with a closure piece across the outer limbs so as to complete two other separate paths for said magnetic circuits; and wherein the clearance between the ends of said fixed poles and the periphery of said wheel is small enough to provide magnetic circuits of low leakage.
 6. An electromagnetic oscillator according to claim 1, in which a diode is connected between the emitter and base of said transistor.
 7. An electromagnetic oscillator comprising in combination a movable and a fixed element, an electrical device for sustaining the oscillation of the movable element, said movable and said fixed elements forming at least one deformable magnetic circuit the remanence of which is utilized in the function of said device, a reading and a driving coil, Said reading coil being associated with a first fixed pole of a first deformable magnetic circuit, and said driving coil being associated with a second fixed pole of a second deformable magnetic circuit, a third and a fourth fixed pole associated with a third and a fourth deformable magnetic circuit respectively, the third and fourth fixed poles each being situated on opposite sides of the fixed element and being between the first and second fixed poles, an electronic switching element comprising a transistor having a base, and an emitter collector junction the impedance of which depends on the value of a reading signal derived from said reading coil, and supplied to said base, and wherein said reading coil is connected between said base and a ground, and said driving coil is connected in series with said emitter-collector junction, a direct source of electrical current, and said ground; said source inducing a driving signal in said driving coil whereby an electromagnetic force is applied between said driving coil and said movable element to impart motion thereto.
 8. An electromagnetic oscillator according to claim 7 in which said movable said fixed element cooperate in the same plane.
 9. An electromagnetic oscillator according to claim 7 in which said direct source of electrical current induces the driving signal in said reading coil in the form of a pulse of energy, and after said pulse the remanent flux in said magnetic circuit induces said reading signal in said reading coil, the inductions repeating in a manner in a respective sequence so as to maintain said oscillation; said driving coil being connected between said direct source of electrical current and the collector of said transistor, said reading coil being connected between the base of said transistor and said ground, and the emitter of said transistor being connected to said ground.
 10. An electromagnetic oscillator according to claim 7 in which said fixed element is a frame of ferromagnetic material, said fixed first, second, third and fourth poles being made of ferromagnetic material and integral with said frame, and said movable element is a balance wheel pivoted reciprocally to rotate within the boundaries of said frame, and having at least two peripheral prominences spaced apart on the periphery of said wheel, the spacing of the projecting ends of said first and third fixed poles, and said wheel also having at least one open slot in its periphery located between said prominences in a position which causes said slot to be substantially adjacent the projecting end of the second fixed pole when said wheel is rotated so that said prominences are each adjacent the projecting ends of said first and third fixed poles, said first, second, third and fourth fixed poles forming respective paths for a plurality of deformable magnetic circuits passing through said frame and said wheel, and wherein said frame forms a continuous outer path, said fourth fixed pole is a substantially scimitar-shaped, integral portion of said outer path and extends over a distance corresponding approximately to a third of the periphery of the wheel, said first, second and third fixed poles projecting inwardly of said continuous outer path and terminating with a small clearance between the ends thereof and the periphery of said wheel, said clearance and the clearance between the fourth fixed pole and the periphery of the wheel being small enough to provide said magnetic circuits having low leakage.
 11. An electromagnetic oscillator according to claim 7, in which a diode is connected between the emitter and base of said transistor.
 12. An electromagnetic oscillator comprising in combination a movable and a fixed element, an electrical device for sustaining the oscillation of the movable element, said movable and said fixed elements forming at least one deformable magnetic circuit the remanance of which is utilized in the function of said device, a reading and a driving coil, constituting part of said electrical device, which devIce comprises a single tapped coil wherein the turns between one end of said coil and the tapping constitute said reading coil, and the turns between the tapping and the other end of said coil constitute said driving coil, said tapped coil being mutually associated with one of the fixed poles of said circuit, an electronic switching element which is a transistor having a base, and an emitter-collector junction the impedance of which depends on the value of a reading signal derived from said reading coil, and wherein one end of said tapped coil is connected in series with said emitter-collector junction, a direct source of electrical current, and a ground, the other end of said tapped coil being connected to said ground, an autotransformer constituting a single coil with an intermediate tapping, said coil being connected between the base of said transistor and said ground, said intermediate tapping being connected to the tapping on said tapped coil; said intermediate tapping on said autotransformer being located such that the reading signal derived from the reading coil is amplified by a predetermined value by said autotransformer to generate a signal which when supplied to the base of said transistor causes the emitter-collector junction to become conductive, said source inducing a driving signal in said driving coil whereby an electromagnetic force is applied between said driving coil and said movable element to impart motion thereto.
 13. An electromagnetic oscillator according to claim 12, in which a diode is connected between the emitter and base of said transistor.
 14. In a device for the maintenance of the oscillations of nonpolarized electromagnetic oscillators having a regulating unit associated with a deformable magnetic circuit to which a control pulse is applied through the intermediary of a silicon transistor, at least one motor coil associated with a fixed pole of the magnetic circuit; at least one reading coil, associated with a fixed pole of the circuit; the motor coil being mounted between a source of low voltage direct current and the collector of a transistor, the reading coil being mounted between the base of said transistor and the ground, the emitter of the transistor being grounded, the base of said transistor being connected to the mass of the electromagnetic oscillator through the winding of an autotransformer, the intermediary tap of which is connected to an intermediary point of a winding surrounding a fixed pole of the magnetic circuit, one of the extremities of said winding being connected to said mass while the other extremity is connected to the emitter of the transistor, the collector of which is connected to polarization elements of the oscillator, the first parts of the two above mentioned windings connected to the mass comprising a number of turns calculated to establish a specific amplification ratio with the number of turns of the second parts of the windings connected to the transistor, the winding surrounding the fixed pole of the magnetic circuit thus serving both as motor coil and reading coil.
 15. In a device according to claim 14, a diode inserted between the terminals of the base and of the emitter of the transistor between the motor coil and the autotransformer so as to prevent the amplifying unit from acting as an oscillator and to protect the emitter-base function of the transistor by short-circuiting induced reverse voltage originating in the motor coil and the portion of the autotransformer connected to the mass and located beyond the point of junction with said motor coil.
 16. In a device according to claim 14, a voltage transformer amplifying the reading voltage. 